For most of human history, we have received most of our energy from sunshine, fire, muscle power, and wind. With the industrial revolution, coal-fired steam engines quickly gave way to petroleum-based fuels and internal combustion engines. When electricity came into use, it was produced by either hydropower, or some type of thermal plant that utilized steam produced by nuclear, coal, or natural gas to spin a turbine connected to a generator.
Things remained that way for about a hundred years until two events signaled the need for change. First, events in the Middle East led to an oil embargo, which made it clear that inexpensive oil was not something that could be taken for granted. That started a movement to develop more efficient vehicles, while research into other ways of powering our society got underway. The second was the growing awareness that increased concentrations of CO2, a byproduct of fossil fuel combustion, is trapping heat in the atmosphere and altering global climate in a highly disruptive way.
These led to a search for new energy sources that would be both emission-free and renewable. After a slow start, renewable power sources, particularly solar and wind, have experienced remarkable growth.
The Growth of Wind Power
In the period from 2005 to 2015, wind power grew from 9,121 MW to 73,992 MW. That’s more than an eight-fold increase. Wind’s contribution has grown from 0.9% of total generation capacity to 6.4%. There are a number of factors behind this growth. Government policies and incentives led to substantial R&D efforts, which got the engines of innovation running. As sales picked up, more companies entered the race. Costs came down, lessons were learned, efficiencies improved. As turbine size and capacity grew, they crossed a critical threshold where wind became cost-competitive with more conventional power sources.
As of February 2017, wind power became the largest renewable source with 82,000 MW, outpacing hydropower for the first time. Turbines of 0.1MW have now given way to giant 8MW turbines for offshore generation. Larger turbines produce more because winds are stronger at the higher elevations that the giant blades can reach.
The Ascent of Solar Power in Energy Technology
While solar got off to a slower start, it has the potential to eventually outpace wind. Solar development has split into two primary branches: solar thermal and solar photovoltaic. Solar thermal follows the same pathway as wind and most other electricity sources in that a spinning generator ultimately produces the electricity. However, solar thermal uses the sun’s rays rather than burning fuel to produce the steam.
Concentrating mirrors focus many beams of sunlight onto a receiver containing a working fluid that is heated enough to produce steam that spins a turbine when released. This concentrated solar power (CSP) works best at large scale and is therefore best suited for utility-scale distribution. One advantage of this type of solar power is that the working fluid can remain hot for several hours after the sun has set, continuing to produce power during that time.
Solar photovoltaic or solar PV is based on the use of semiconductors to convert sunlight directly into electricity. The modules are small and can be placed anywhere. Developed initially for the space program, these materials were too expensive and inefficient for commercial purposes. However, like wind, they too have benefited from a tremendous amount of technical innovation. Unlike most other forms of energy generation, they have no moving parts, which means that they can be expected to be especially reliable.
During the same 2005-15 time period, combined solar thermal and solar PV grew from 588 MW to 27,394 MW. That’s more than a 46-fold increase. While that still represents slightly less than 2% of all electric capacity, if that growth rate continues, it will eventually outstrip all other sources. Back in 1977, the cost of solar energy was $76.67 per watt. As of 2013, that price was $0.74. That’s over a one-hundred-fold decrease. Today’s prices have fallen even further, even as performance has increased. A lot of the technological breakthroughs of the past decade, like nanotechnology have directly benefited solar PV.
While it’s true that solar and wind are intermittent sources, the onset of economical storage and a highly connected smart grid that can receive power wherever it is available will substantially address those concerns.
While renewables were originally developed in response to one specific set of requirements, development has been so successful that they now offer, in many cases, the least expensive option. As a result, in the years ahead we can expect to see a world that is predominantly powered by non-polluting clean, energy whose sources will never run out.